As described in U.S. Pat. No. 7,374,282 issued to Robert K. Tendler on May 20, 2008, it is desirable to provide sunglass lenses with a polarization gradient such that when one views the far field one looks at a polarized scene, whereas when one looks at the near field where a polarized display might be located one sees the polarized display without it being blackened by cross polarization.
As described in the aforementioned patent, one of the ways of providing for gradient polarization in which there is maximum polarization at the top of the lens and minimum polarization at the bottom of the lens is to provide differential stretching of the oriented material which is provided with a stain, such as iodine or a dichroic dye. This then provides the final structure with a gradient polarization characteristic.
However this type of technique is difficult to achieve and while there may be many other ways of providing for gradient polarization for a polarized sheet, there remains the problem in providing a true gradient polarized lens. Moreover there are problems in providing for gradient lenses in which the color or filter characteristics of the lens vary across the face of the lens.
It will be appreciated that if one can provide a gradient polarized lens with printable characteristics, it would be very easy to fashion specialty lenses having required specialized characteristics simply by printing.
As to printing to provide polarized films with either a transparency image or a printed image, inkjet printing has been used to produce 3-D viewable images by overprinting polarized material or films with dichroic dyes or other colorants. In one embodiment their 3-D imaging involves printing on one side of an oriented film with one image and an offset version of the same image on the opposite side of the film. When viewed stereoscopically with oppositely circularly polarized glasses, one sees a 3-D image of the artwork printed on the polarized film due to the offset in the images front and back. Inkjet printing of oriented substrates has been described in U.S. Pat. Nos. 5,552,182; 5,591,508; 5,758,036; 5,764,248; 6,013,123; and 6,347,851 issued to Julius J. Scarpetti, all incorporated herein by reference. It will be appreciated that nowhere in the Scarpetti patents is suggested providing a transparency involving an oriented substrate with a gradient pattern, either for providing a gradient polarization characteristic or for providing color filtering characteristics.